Melt blown and spunbond webs typically comprise insoluble and nondegradable polymers such as water insoluble polyethylene, polypropylene, polyester and polyamide. Such webs are used in the manufacture of a variety of disposable products such as disposable diapers, feminine napkins, surgical gowns, laundry bags, bed pads, and the like. Such articles are designed to absorb and contain bodily fluids and/or provide a physical barrier to such fluids. Water soluble and biodegradable nonwoven webs may provide some solutions to environmental concerns regarding the disposal of such items.
Heat fusible webs are used for a variety of uses. In the textile industry, heat fusible webs are used to hold pieces of fabric, such as a patch pocket, in place prior to being sewn. These heat fusible webs are also used to create hems on pants or for a variety of ornamental craft appliques. Webs currently available for such uses are typically low viscosity at application temperature and insoluble in water. Upon activation with heat these materials often soak into the fabric workpiece causing the fabric to become stiff. Often the melted web soaks in to the extent that it fails to form the intended bond and reapplication is necessary.
A water soluble nonwoven comprising polyvinyl alcohol (PVOH) is taught in Dever et at., JP 59041260. Modifying the rate of water solubility of a PVOH based melt blown material using two different chemical treatments is described in the Development and Evaluation of Water Soluble Melt Blown Nonwovens, Dever, Benson, and Pair, INDA JNR, Vol. 5, No. 2, published 1993.
PVOH as a base polymer for the formation of a water soluble web suffers from several disadvantages. Due to its high melt point and poor thermal stability, it is very difficult to thermally process. An extruder, rather than merely a melt tank, is required to process the PVOH into a web. Additionally, once the web is formed, it has poor heat seal properties such that it would need to be heat sealed at temperatures that adversely affect the integrity of the substrate.
Water soluble polyamide prepared from adipic acid and polyoxyethylene diamine is reported by Fagerberg et al., U.S. Pat. No. 3,882,090 and Speranza et al., U.S. Pat. Nos. 5,086,162, 5,324,812 and 5,118,785. However, no such compositions have been used to form a water soluble nonwoven web or combined with other fibers to form nonwoven webs exhibiting a variety of properties.
The applicants have found that certain water soluble polyamides exhibit improved melting characteristics for manufacturing spunbond and melt blown nonwoven webs.